Vitamin E compounds (tocotrienols and tocopherols) are attracting attention as substances with health functionality and high antioxidant activity. In particular, tocotrienols have the same basic structure as tocopherols, but with three double bonds in their side chains, and thus have approximately 50 times higher antioxidant activity than tocopherols (Non-patent Reference 1). Recently, it has been reported that tocotrienols have high bioactivity, such as improvement arteriosclerosis and anti-cancer effects (Non-patent Reference 2), and there are expectations for active use in the pharmaceutical and food fields.
However, whereas tocopherols are contained in a wide-range of vegetable oils such as soy bean, rapeseed, sunflower, corn and so on, tocotrienols are contained at ultra-low concentration in certain vegetable oils such as palm. rice bran and so on. In addition, tocotrienols tend to decompose by oxidation due to the double bonds of their side chains, and easily lose their bioactivity.
Deodorizer distillate (scum oil) discharged in the deodorization process during manufacturing of edible oil is used as the raw material for separating and recovering these vitamin E compounds. Although, in all cases, the amounts of vitamin E compounds contained in scum oil are a few tens of times higher than the crude oil, the main component is free fatty acids, and scum oil also contains triglycerides, sterols and various hydrocarbons.
Therefore, no matter which vitamin E compounds are the target, there needs to be a process for recovering rich fraction of vitamin E compounds (corresponding to rough fractionation of vitamin E compounds) separated from raw materials, and a process for obtaining high-purity vitamin E compounds by further separating vitamin E compounds in the recovered solution from other contaminants. Various chromatographic separation methods have been proposed for the latter high-level separation process, and when necessary it is possible to separate the α, β, γ and δ isomers of tocopherol and tocotrienol by trying them chromatographic separation method.
However, for the rich fraction of vitamin E compounds recovered in the former process: the content of vitamin E compounds is low, the amount of contaminants such as free fatty acids is much, and (as issues specific to the chromatographic separation) it requires a large amount of eluent and a long elution-operative time, as specific issues to the chromatographic separation. As results, the production cost and environmental load of the waste liquid had increasingly been problems. Regarding the recovery process for vitamin E compounds, various studies have previously been carrying out focusing on tocopherols. For example, the molecular distillation method has already reached the stage of industrialization.
However, if the molecular distillation method is applied to deodorizer distillate derived from rice bran or palm containing tocotrienols, there is a large thermal decomposition loss due to distillation. Thus there was a problem because the recovered amount of tocotrienol and its purity were extremely low. (Japanese Unexamined Patent Application Publication No. 1996-100131, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 1998-508605, Japanese Unexamined Patent Application Publication No. 2002-194381, Japanese Unexamined Patent Application Publication No. 2002-3488, Japanese Unexamined Patent Application Publication No. 2003-171376, Japanese Unexamined Patent Application Publication No. 2004-305155, Japanese Unexamined Patent Application Publication No. 2005-536191, Japanese Unexamined Patent Application Publication No. 2007-521382, Japanese Unexamined Patent Application Publication No. 2007-176801).
On the other hand, the inventors have developed a method for simultaneously producing tocotrienols and biodiesel fuel from fats and oils (Patent Reference 1). Patent Reference 1 discloses a method for manufacturing vitamin E compounds from the fats and oils, including separation by adsorption of vitamin E compounds contained in fats and oils to an anion exchanger, and thereafter, desorption and recovery from the anion exchanger. This method requires no molecular distillation process, and thus can prevent decomposition of vitamin E compounds such as tocotrienols.
However, the method disclosed in Patent Reference 1 had the problem that free fatty acids remained as impurities in the rich fraction of vitamin E compounds.